1. Technical Field of the Invention
The various embodiments of the present invention relates in general to a semiconductor package and, more particularly but not by way of limitation, to a semiconductor package in which the adhesiveness between a chip paddle and a package body is improved, and the chip paddle ground-bonding is improved.
2. History of Related Art
It is conventional in the electronic industry to encapsulate one or more semiconductor devices, such as integrated circuit dies, or chips, in a semiconductor package. These plastic packages protect a chip from environmental hazards, and provide a method of and apparatus for electrically and mechanically attaching the chip to an intended device. Recently, such semiconductor packages have included metal leadframes for supporting an integrated circuit chip which is bonded to a chip paddle region formed centrally therein. Bond wires which electrically connect pads on the integrated circuit chip to individual leads of the leadframe are then incorporated. A hard plastic encapsulating material, or encapsulant, which covers the bond wire, the integrated circuit chip and other components, forms the exterior of the package. A primary focus in this design is to provide the chip with adequate protection from the external environment in a reliable and effective manner.
As set forth above, the semiconductor package therein described incorporates a leadframe as the central supporting structure of such a package. A portion of the leadframe completely surrounded by the plastic encapsulant is internal to the package. Portions of the leadframe extend internally from the package and are then used to connect the package externally. More information relative to leadframe technology may be found in Chapter 8 of the book Micro Electronics Packaging Handbook, (1989), edited by R. Tummala and E. Rymaszewski and incorporated by reference herein. This book is published by Van Nostrand Reinhold, 115 Fifth Avenue, New York, N.Y.
Once the integrated circuit chips have been produced and encapsulated in semiconductor packages described above, they may be used in a wide variety of electronic appliances. The variety of electronic devices utilizing semiconductor packages has grown dramatically in recent years. These devices include cellular phones, portable computers, etc. Each of these devices typically includes a motherboard on which a significant number of such semiconductor packages are secured to provide multiple electronic functions. Not only are semiconductor chips highly integrated, but also semiconductor packages are highly miniaturized with an increased level of package mounting density.
According to such miniaturization tendencies, semiconductor packages, which transmit electrical signals from semiconductor chips to motherboards and support the semiconductor chips on the motherboards, have been designed to have a small size. By way of example only, such semiconductor packages may have a size on the order of 1×1 mm to 10×10 mm. Examples of such semiconductor packages are referred to as MLF (micro leadframe) type semiconductor packages and MLP (micro leadframe package) type semiconductor packages. Both MLF type semiconductor packages and MLP type semiconductor packages are generally manufactured in the same manner.
However, this conventional semiconductor package is problematic in that a thickness of the silver plated layer formed on the upper faces of the chip paddle and the internal leads deteriorates the adhesiveness between the package body and the chip paddle or the internal leads. That is, the silver-plated layer is very weakly bonded to the package body of the encapsulation material (the chip paddle or the side of the internal lead, both of which are made of copper, are strongly bonded to the package body), so that interfacial exfoliation is easily caused at the boundary between the package body and the silver-plated layer. Further, moisture can readily permeate the semiconductor package through the exfoliated portion, which may cause the semiconductor package to crack.
Usually a semiconductor chip or a chip paddle is ground-bonded by conductive wires to achieve grounding or eliminate electrical noise problems. In this conventional semiconductor package, the semiconductor chip is similar in area to the chip paddle, so that there are no sufficient areas for ground bonding.